Optical fiber, optical cable, and hydrogen production device comprising optical cable

ABSTRACT

An optical fiber including a light guiding inner core. The light guiding inner core includes a first light guiding segment and a second light guiding segment connected to the first light guiding segment. The first light guiding segment includes, from the inside out, a light absorbing layer, an inner electrode layer, an insulating layer, a void layer, a proton exchange membrane, and an outer electrode layer. The void layer is formed between the insulating layer and the proton exchange membrane. The light absorbing layer is a photovoltaic material layer. The inner electrode layer communicates with the proton exchange membrane via a plurality of microelectrodes across the insulating layer and the void layer. The plurality of microelectrodes is evenly disposed around the inner electrode layer. The outer electrode layer is a porous conductive structure. The second light guiding segment of the light guiding inner core includes a conductive layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International Patent Application No. PCT/CN2017/096154 with an international filing date of Aug. 7, 2017, designating the United States, now pending, and further claims foreign priority benefits to Chinese Patent Application No. 201610947824.9 filed Oct. 26, 2016. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, Mass. 02142.

BACKGROUND

The disclosure relates to an optical fiber, an optical cable, and a hydrogen production device comprising the optical cable that can utilize solar energy to produce hydrogen.

Conventional hydrogen production devices use electrical energy to split water into hydrogen and oxygen. There are two main technologies available on the market, alkaline and proton exchange membrane (PEM) electrolyzers. Alkaline electrolyzers are cheaper in terms of investment, but less efficient. Conventional alkaline electrolysis has an efficiency of only about 70%, defined as energy consumed per standard volume of hydrogen produced (MJ/m³).

SUMMARY

The disclosure provides an optical fiber, an optical cable, and a hydrogen production device comprising the optical cable that are efficient in utilizing solar energy to produce hydrogen.

Disclosed is an optical fiber comprising a light guiding inner core. The light guiding inner core comprises at least a first light guiding segment and a second light guiding segment connected to the first light guiding segment. The first light guiding segment comprises a light-transmitting circumferential wall; the second light guiding segment comprises alight-transmitting or opaque circumferential wall; the first light guiding segment comprises, from the inside out, a light absorbing layer, an inner electrode layer, an insulating layer, a void layer, a proton exchange membrane, and an outer electrode layer. The void layer is formed between the insulating layer and the proton exchange membrane. The light absorbing layer is a photovoltaic material layer. The inner electrode layer communicates with the proton exchange membrane via a plurality of microelectrodes across the insulating layer and the void layer. The plurality of microelectrodes is evenly disposed around the inner electrode layer. The outer electrode layer is a porous conductive structure; the second light guiding segment of the light guiding inner core comprises a conductive layer; and the conductive layer is connected to the inner electrode layer.

In use, the first light guiding segment of the optical fiber is immersed in an electrolytic cell containing an electrolyte; the second light guiding segment and the outer electrode layer are respectively connected to the positive and negative electrodes of an external power supply or indirectly connected through grounding to form an electrolyzer; the light energy introduced by the light guiding inner core excites the light absorbing layer to generate electrons to form a photovoltaic cell, which can supplement the consumed electrical energy.

The conductive layer is integrated with and is of the same material as the inner electrode layer.

The light guiding inner core further comprises a third light guiding segment connected to the second light guiding segment; the third light guiding segment comprises an opaque circumferential wall.

The inner electrode layer of one end of the first light guiding segment away from the second light guiding segment is covered and sealed with the insulating layer, or one end of the first light guiding segment away from the second light guiding segment is covered and sealed with the insulating layer. Insufficient sealing may result in the leakage of electrical energy. However, the catalysis reaction is mainly concentrated on the microelectrodes of which the exposed area is small, so that the leakage loss is small and the electrochemical reaction can still be implemented.

The light absorbing layer has a thickness of 50 nm to 20 μm, the inner electrode layer has a thickness of 50 nm to 50 μm, the insulating layer has a thickness of 10 nm to 50 μm, the microelectrode has a radius of 100 nm to 20 μm, and the proton exchange membrane has a thickness is 0.05-0.5 mm.

The light guiding inner core is of a material such as a quartz fiber, a plastic optical fiber, a crystal fiber, a polymer material light pipe, a glass light pipe, a glass fiber or a transparent mica fiber, which can transmit light with high-throughput along the surface. The light guiding inner core is of an elongated linear shape, solid or hollow, and its cross-sectional area may also be circular and rectangular (such as a light guiding tape).

The plurality of microelectrodes is a Platinum (Pt) electrode, a Palladium (Pd) electrode, or an iron (Fe) electrode containing NiS. The microelectrodes are across the insulating layer by photolithography and communicate with the inner electrode layer. The microelectrodes can be regarded as an extension of the inner electrode layer, which increases the reaction area of the inner electrode and plays a catalytic role.

When the inner electrode layer or the outer electrode layer is used as a cathode, the material is Platinum (Pt), Palladium (Pd), Copper (Cu), aluminum (Al), Graphene, Titanium (Ti), Thallium (Tl), Chromium (Cr), or Gold (Au). When the electrode layer is used as an anode, the material is C or Ni carrying a catalyst. The catalyst is an iron oxide, a cobalt oxide, a nickel oxide, or a mixture thereof. The optical fiber of the disclosure is divided into two types according to the position of the anode and the cathode: the first is that the cathode is inside (i.e., the inner electrode layer), the anode is outside (i.e., the outer electrode layer); the second is that the anode is inside and the cathode is outside; when connecting to an external power supply, the cathode is connected to the negative pole and the anode is connected to the positive pole.

The light absorbing layer is of an organic dye in the form of a divalent phosphonium salt of dicarboxybipyridine coated on the surface of the light guiding inner core through metal organic vapor deposition or chemical vapor deposition, preferably, chemical vapor deposition; or an organic dye is mixed with an organic viscose under vacuum to form the light absorbing layer on the surface of the light guiding inner core.

The light absorbing layer is of an inorganic semiconductor material coated on the surface of the light guiding inner core through vacuum spraying, vacuum sputtering, thermal evaporation or physical vapor deposition; the inorganic semiconductor material is TiO₂, ZnS, CdSe, MoS, CuInS or GaInP; preferably n-type TiO₂, ZnS or CdSe quantum dots having a particle diameter of 5 to 10 nm, and the three-dimensional scale is on the order of nanometers (0.1 to 100 nm).

The insulating layer is of silicon dioxide, silicon nitride, polyimide or parylene.

The proton exchange membrane is a perfluorosulfonic acid membrane (Nifion membrane), a sulfonated polystyrene membrane, a modified perfluorosulfonic acid polymer membrane, or 1-butyl-3-methylimidazolium trifluoromethanesulfonate membrane.

The electrolyte is water, an acidic solution, an alkaline solution or an aqueous solution containing an electrolytic activator; the acidity and basicity of the electrolyte shall be based on the bearing capacity of the proton exchange membrane.

The disclosure also provides an optical cable comprising a protective sleeve and a plurality of optical fibers axially disposed in the protective sleeve.

The plurality of optical fibers in the protective sleeve are bundled. When the outmost layer of the optical cable is cut open and the outermost optical fiber is connected to an external power supply, all the optical fibers are meant to connect to the external power supply. This simplifies the connection of the optical fibers to the power supply.

The disclosure also provides a device for hydrogen production by photoelectric hydrolysis of water, which comprises an electrolytic cell, an optical cable, an internal electrode converger, an external electrode converger and a fiber dispersing device. The optical cable extends into the electrolytic cell to electrolyze water to produce hydrogen; one end of the first light guiding segment of the optical fiber away from the second light guiding segment is exposed out of the protective sleeve of the optical cable; one end of the second light guiding segment of the optical fiber away from the first light guiding segment is exposed out of the protective sleeve of the optical cable; the first light guiding segment of the optical fiber is dispersed by the fiber dispersing device and immersed into the electrolyte, and the outer electrode layer of the first light guiding segment is electrically connected to the external electrode converger; the second light guiding segment of the optical fiber is disposed outside the electrolytic cell, and the conductive layer of the second light guiding segment is electrically connected to the internal electrode converger.

A plurality of optical cables is disposed above the electrolytic cell in arrays.

The fiber dispersing device comprises a first aperture plate and a second aperture plate fixedly disposed on an upper part and a lower part of the electrolytic cell, respectively. The first aperture plate comprises a plurality of first through holes in arrays, and the second aperture plate comprises a plurality of second through holes in arrays corresponding to the first through holes in arrays; the first light guiding segment of each of the optical fibers is fixed on the first aperture plate and the second aperture plate via the first through holes and the second through holes.

The first aperture plate is insulated; the second aperture plate is conductive and used as the external electrode converger communicating with the outer electrode layer of the first light guiding segment of each optical fiber. The internal electrode converger is a copper ring sheathed on one end of the second light guiding segment of the optical fiber, and is in contact with the conductive layer.

The electrolytic cell is provided with a defoaming net.

To determine whether an electrochemical process has practical economic value, the conversion rate, current efficiency, power consumption and space time yield are measured and evaluated. By introducing new materials, optimizing structural design and improving index parameters, the method of hydrogen production from electrolysis of water is of great economic value.

To explain the work principle of the hydrogen production device of the disclosure, the principle of electrolyzed water is given below:

1) Reaction Principle

When water is electrolyzed in an acidic solution,

Cathode:2H⁺+2e→H₂φ⁰=1.23V

Anode:H₂O→½O₂+2H++2e φ ⁰=1.23 V

When water is electrolyzed in an alkaline solution,

Cathode:2H₂O+2e→H₂+2OH⁻ φ⁰=−0.83V

Anode:2OH⁻→½O₂+H₂O+2e φ ⁰=0.4V

Total Electrode Reaction:

H₂O→H₂+½O₂ φ⁰=1.23V

2) Voltage of Electrolytic Cell

Theoretical decomposition voltage E_(d)

Oxygen overpotential h_(oxygen)

Hydrogen overpotential h_(hydrogen)

Ohmic pressure drop of solution IR_(solution)

Ohmic pressure drop of diaphragm IR_(diaphragm)

Bubble effect pressure drop IR_(gas)

Ohmic voltage drop of the electrode IR_(u)

Cell voltage (total) V=E_(d)+h_(oxygen)+h_(hydrogen)+ΣIR

The equation indicates that when the current efficiency is constant, the magnitude of the voltage determines how much power is consumed.

When the reaction conditions are constant, the decomposition voltage E_(d) of hydrogen produced by electrolysis of water is a fixed value and is mainly supplied by an electric field. The photocatalytic material is used to give the electrolysis electrode the certain voltage compensation, and the supplemental energy is provided by the solar energy to reduce the power consumption.

The overpotential of hydrogen and oxygen is related to the material. Choosing a low hydrogen overpotential and low oxygen overpotential material can reduce the power consumption. Due to low hydrogen and oxygen overpotential materials such as Pt, Pd, Co, Ni, Cu and other metal materials, most of them are precious metals and expensive. The size of the microelectrodes is very small and the amount of material used is small.

Ohmic Pressure Drop IR_(solution) of Solution: Reduces solution resistance by using a “zero gap” proton exchange membrane.

Pressure drop IR IR_(gas) of bubble effect: The porous material is used to reduce the surface tension of the bubble and reduce the amount of bubble generation, thereby reducing the pressure drop of the bubble effect.

Electrode ohmic voltage drop IRu, from the relationship between current and electrode radius

${i = {{nFc}^{o}{D\left\lbrack {{2{r^{2}\left( \frac{p}{Dt} \right)}^{1/2}} + {2{pr}}} \right\rbrack}}},$

it can be seen that when the current reaches a steady state, the smaller the electrode radius, the smaller the current. At this point, the electrode ohmic voltage drop can be ignored and no further voltage debugging is required. The reference electrode can be omitted and the design space of the electrolytic cell can be saved.

Use microelectrode, membrane, porous material and other techniques to reduce the design reactor cell volume Using a plurality of microelectrode array arrangements, electrons are transferred along the metal surface, increasing the electrode area A, increasing the space time yield A/V value, and increasing the amount of product obtained per unit volume of the electrolytic cell per unit time.

Advantages of the disclosure are summarized as follows: 1) solar energy is utilized to supplement electrical energy, reducing power consumption and increasing space-time yield of hydrogen. 2) The diameter of the optical fiber is small, and the specific surface area of the electrode reaction is large, which can reduce the consumption of materials, reduce the cost. 3) The hydrogen production device comprises a plurality of optical cables arranged in arrays on the electrolytic cell, which ensures the efficiency of hydrogen production. 4) The electrical energy efficiency can reach 90%, and the space-time yield A/V can reach 200 cm⁻¹. 5) The electrodes are in the form of optical fiber and optical cable, which is easy to mass-produce, easy to use, and can increase or decrease the scale of hydrogen production as needed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a device for hydrogen production by photoelectric hydrolysis water in examples 1 to 4.

FIG. 2 is a cross-sectional view of an optical cable of the device for hydrogen production of FIG. 1.

FIG. 3 is a longitudinal cross-sectional view of the optical fiber in FIG. 2.

FIG. 4 is a cross-sectional view of a first light guiding segment of the optical fiber of FIG. 3.

FIG. 5 is a top view of an upper/second aperture plate in FIG. 1.

FIG. 6 is a top view of a device for hydrogen production by photoelectric hydrolysis of water in example 5.

FIG. 7 is a schematic diagram showing an electrolysis principle of a single optical fiber of FIG. 3.

In the drawings, the following reference numbers are used: optical fiber 1, first light guiding segment A, second light guiding segment B, third light guiding segment C, light guiding inner core 2, light absorbing layer 3, inner electrode layer 4, insulating layer 5, void layer 6, microelectrode 7, proton exchange membrane 8, outer electrode layer 9, conductive layer 10, optical cable 11, protective sleeve 12, electrolytic cell 13, electrolyte 14, copper ring connected to cable interface 15, auxiliary positioning net 16, first aperture plate 17, second aperture plate 18, through hole 19, defoaming net 20, gas outlet 21, water inlet 22, water outlet 23, wastewater outfall 24, external power supply 25, wire 26.

DETAILED DESCRIPTION

The disclosure will be further described in detail below with reference to the drawings and specific examples.

Example 1

As shown in FIG. 1 to FIG. 5, the device for hydrogen production by photoelectric hydrolysis of water provided in this example comprises an electrolytic cell 13, an optical cable 11, an internal electrode converger, an external electrode converger, and a fiber dispersing device. The various parts are specified as follows:

The optical cable 11 comprises a protective sleeve 12 and a plurality of bundled optical fibers 1 axially arranged in the protective sleeve 12.

The optical fiber 1 comprises a light guiding inner core 2, and the light guiding inner core 2 is sequentially divided into three parts: a first light guiding segment A, a second light guiding segment B, and a third light guiding segment C.

The first light guiding segment of the light guiding inner core 2 comprises a light-transmitting circumferential wall; the second and third light guiding segments comprises an opaque circumferential wall. The first light guiding segment A of the light guiding inner core 2 comprises, from the inside to the outside: a light absorbing layer 3, an inner electrode layer 4, an insulating layer 5, a proton exchange membrane 8 and an outer electrode layer 9; and a void layer 6 is formed between the insulating layer 5 and the proton exchange membrane 8. The inner electrode layer 4 communicates with the proton exchange membrane 8 via a plurality of microelectrodes 7 across the insulating layer 5 and the void layer 6. The plurality of microelectrodes 7 are arranged around the inner electrode layer 4 in arrays. The outer electrode layer 9 is a porous conductive structure. The inner electrode layer 4 at the front end of the first light guiding segment A is covered and sealed by the insulating layer 5. The light guiding inner core 2 is provided with a conductive layer 10 in the second light guiding segment B, and the conductive layer 10 is obtained by extending the inner electrode layer 4 to the second light guiding segment B. The light absorbing layer 3 remains in the second light guiding segment B for ease of production and manufacturing. That is, the second light guiding segment B comprises the portions corresponding to the inner electrode layer 4 and inside the inner electrode layer 4 of the first light guiding segment A, and the portions corresponding to the insulating layer 5 and outside the insulating layer 5 of the first light guiding segment A are removed. The third light guiding segment C comprises only the light guiding inner core 2.

The light guiding inner core 2 is made of a quartz fiber having a high-throughput light transmission along the surface, and an anti-reflection membrane is plated on the third light guiding segment C. The outer electrode layer 9 serves as an anode, and the material thereof is a porous carbon layer carrying an iron oxyhydroxide catalyst. The inner electrode layer 4 serves as a cathode, which comprises a layer of conductive Cu having a thickness of 500 nm for transmitting a power supply current and collecting an electron current generated by the light absorbing layer 3. The n-type TiO₂ is selected as the material of the light absorbing layer 3, and a light absorbing layer 3 having a thickness of 500 nm is formed by vacuum spraying on the light guiding inner core 2. The material of the insulating layer 5 is silicon dioxide and had a thickness of 1 μm. The material of the microelectrode 7 is Pt, and the radius is set to 100 nm. The microelectrodes 7 distributed in an array in the insulating layer 5 are prepared by photolithography. The proton exchange membrane 8 selects a Nifion membrane having a thickness of 0.1 mm, which allows the proton conduction and isolates oxygen and hydrogen.

The optical cable 11 penetrates and is fixed from the top of the electrolytic cell 13, and one end of the first light guiding segment A is immersed in the electrolyte 14 in the electrolytic cell 13. The protective sleeve 12 of the optical cable 11 on one end of the first light guiding segment A and the second light guiding segment B is cut to expose the optical fiber 1. One end of the first light guiding segment A of the optical fibers 1 is dispersed and immersed in the electrolytic 14 by a fiber dispersing device, and the outer electrode layer 9 of each of the optical fibers 1 is electrically connected to the external electrode converger. In the second light guiding segment B, the conductive layer 10 of each optical fiber 1 is electrically connected to the internal electrode converger.

The fiber dispersing device comprises a first aperture plate 17 and a second aperture plate 18 that are fixedly disposed on the upper part and the lower part of the electrolytic cell 13. The first aperture plate 17 comprises a plurality of first through holes 19 in arrays, and the second aperture plate 18 comprises a plurality of second through holes 19 in arrays corresponding to the first through holes in arrays; the first light guiding segment of each of the optical fibers is fixed on the first aperture plate 17 and the second aperture plate 18 via the first through holes and the second through holes 19.

The first aperture plate 17 is an insulator; the second aperture plate 18 is an electrical conductor functioning as an external electrode converger communicating with the outer electrode layer of the first light guiding segment of each optical fiber; the second aperture plate is further connected to the external power source 25 via a wire 26. The internal electrode converger is a copper ring connected to the cable interface and sheathed on the second light guiding segment of the bundled optical fiber, and is in contact with the conductive layer. The copper ring 15 is further connected to the external power source 25 via a wire 26.

The fiber dispersing device comprises a first aperture plate 17, a second aperture plate 18, and through holes 19. An auxiliary positioning net 16 is disposed between the first aperture plate 17 and the second aperture plate 18. The optical fiber 1 passing through the meshes of the positioning net, which enhances the stability of the optical fiber 1 between the two aperture plates.

The electrolytic cell 13 is further provided with a gas outlet 21, a water inlet 22, a water outlet 23, a wastewater outfall 24, and a defoaming net 20. The substances such as H₂ and O₂ produced by electrolysis are output from the gas outlet 21 and further sent to the gas separation system for separation.

To test the working characteristics of the devices, a comparative experiment of hydrogen production by electrolysis of water was carried out under the conditions of no solar irradiation N and sunlight irradiation Y. The experimental lighting conditions were sunlight, and the light intensity was 80,000 lx. The results are as follows:

TABLE 1 Experimental results regarding hydrogen production using optical fibers of the example Specific Current Proton energy Space- density/ Temperature/ Pressure/ Hydrogen Oxygen exchange Voltage consumption/ time Sunlight ma · cm⁻² Voltage/v ° C. atm purity/% purity/% membrane efficiency/% kwhm³h² yield N 1080 1.42 25 1 99.9 99.8 Nafion 87 3.4 200 Y 1080 0.45 25 1 99.9 99.8 Nafion 89 1.07 200

Table 1 shows that in the presence of sunlight, high purity hydrogen can be produced under a relatively low voltage with lower electrical energy consumption.

Example 2

The device for hydrogen production by photoelectric hydrolysis of water is the same as that in Example 1 except that the light guiding inner core 2 is made of a flat light guiding strip and the material of the light absorbing layer 3 is a 5 nm CdSe quantum dot.

To test the working characteristics of the above devices, a comparative experiment of hydrogen production by electrolysis of water was carried out under the conditions of no solar irradiation N and sunlight irradiation Y The experimental lighting conditions were sunlight, and the light intensity was 80,000 lx. The results are as follows:

TABLE 2 Experimental results regarding hydrogen production using optical fibers of the example Specific Current Proton energy Space- density/ Temperature/ Pressure/ Hydrogen Oxygen exchange Voltage consumption/ time Sunlight ma · cm⁻² Voltage/v ° C. atm purity/% purity/% membrane efficiency/% kwhm³h² yield N 1080 1.42 25 1 99.9 99.8 Nafion 87 3.4 200 Y 1080 0.36 25 1 99.9 99.8 Nafion 89 0.87 200

Table 2 shows that in the presence of sunlight, high purity hydrogen can be produced under a relatively low voltage with lower electrical energy consumption.

Example 3

The device for hydrogen production by photoelectric hydrolysis of water provided in this example is the same as that in Example 1, except that the material of the internal electrode layer 4 is replaced by graphene.

To test the working characteristics of the above devices, a comparative experiment of hydrogen production by electrolysis of water was carried out under the conditions of no solar irradiation N and sunlight irradiation Y The experimental lighting conditions were sunlight, and the light intensity was 80,000 lx. The results are as follows:

TABLE 3 Experimental results regarding hydrogen production using optical fibers of the example Specific Current Proton energy Space- density/ Temperature/ Pressure/ Hydrogen Oxygen exchange Voltage consumption/ time Sunlight ma · cm⁻² Voltage/v ° C. atm purity/% purity/% membrane efficiency/% kwhm³h² yield N 1080 1.50 25 1 99.9 99.8 Nafion 82.1 3.6 200 Y 1080 0.42 25 1 99.9 99.8 Nafion 80 1.0 200

Table 3 shows that in the presence of sunlight, high purity hydrogen can be produced under a relatively low voltage with lower electrical energy consumption.

Example 4

The device for hydrogen production by photoelectric hydrolysis of water for the example is the same as that in Example 1 except that the material of the microelectrode 8 is a Fe electrode containing NiS.

To test the working characteristics of the above devices, a comparative experiment of hydrogen production by electrolysis of water was carried out under the conditions of no solar irradiation N and sunlight irradiation Y The experimental lighting conditions were sunlight, and the light intensity was 80,000 lx. The results are as follows:

TABLE 4 Experimental results regarding hydrogen production using optical fibers of the example Specific Current Proton energy Space- density/ Temperature/ Pressure/ Hydrogen Oxygen Exchange Voltage consumption/ time Sunlight mA · cm⁻² Voltage/V ° C. atm purity/% purity/% Membrane Efficiency/% kWhm³h² yield N 1080 1.42 25 1 99.9 99.8 Nafion 87 3.4 200 Y 1080 0.42 25 1 99.9 99.8 Nafion 86 1.0 200

Table 4 shows that in the presence of sunlight, high purity hydrogen can be produced under a relatively low voltage with lower electrical energy consumption.

Example 5

As shown in FIG. 6, the device for hydrogen production by photoelectric hydrolysis of water provided in this example is the same as that in Example 1, except that the number of optical cables 11 is six, and the array distribution (3×2) is on the electrolytic cell 13.

Working Principle:

An electrolytic cell provided with a single light guiding inner core 2 is shown in FIG. 7.

1) The light guiding inner core 2 absorbs light energy in the third light guiding segment C and transmits the light energy to the light absorbing layer 3 of the first light guiding segment A. The light absorbing layer 3 absorbs light energy and generates electrons, which are then transferred to the cathode (internal electrode layer 4). The negative electrode of the external power supply 25 also delivers electrons to the cathode.

2) The water in the electrolyte 14 loses electrons on the anode (the outer electrode layer 9) and generates oxygen and protons, the protons are transferred to the microelectrode 7 through the proton exchange membrane 8, and the protons are combined with electrons on the microelectrode 7 to generate hydrogen gas. Oxygen escapes from the porous anode and hydrogen escapes from the void layer 6. The electrons lost on the anode are transferred to the anode of the external power source 25.

3) The mixed gas of hydrogen and oxygen collected by the electrolytic cell 13 is further separated by a gas separation device.

It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications. 

1. An optical fiber, comprising: a light guiding inner core; the light guiding inner core comprising at least a first light guiding segment and a second light guiding segment connected to the first light guiding segment; the first light guiding segment comprising a light-transmitting circumferential wall; the second light guiding segment comprising a light-transmitting or opaque circumferential wall; wherein: the first light guiding segment comprises, from the inside out, a light absorbing layer, an inner electrode layer, an insulating layer, a void layer, a proton exchange membrane, a plurality of microelectrodes, and an outer electrode layer; the void layer is formed between the insulating layer and the proton exchange membrane; the light absorbing layer is a photovoltaic material layer; the inner electrode layer communicates with the proton exchange membrane via the plurality of microelectrodes across the insulating layer and the void layer; the plurality of microelectrodes is evenly disposed around the inner electrode layer; the outer electrode layer is a porous conductive structure; and the second light guiding segment of the light guiding inner core comprises a conductive layer; and the conductive layer is connected to the inner electrode layer.
 2. The fiber of claim 1, wherein the conductive layer is integrated with and is of the same material as the inner electrode layer.
 3. The fiber of claim 1, wherein the light guiding inner core further comprises a third light guiding segment connected to the second light guiding segment; the third light guiding segment comprises an opaque circumferential wall.
 4. The fiber of claim 1, wherein the inner electrode layer of one end of the first light guiding segment away from the second light guiding segment is covered and sealed with the insulating layer.
 5. The fiber of claim 1, wherein the light absorbing layer has a thickness of 50 nm to 20 μm, the inner electrode layer has a thickness of 50 nm to 50 μm, the insulating layer has a thickness of 10 nm to 50 μm, the microelectrode has a radius of 100 nm to 20 μm, and the proton exchange membrane has a thickness is 0.05-0.5 mm.
 6. The fiber of claim 1, wherein the light guiding inner core is of a quartz fiber, a plastic optical fiber, a crystal fiber, a polymer material light pipe, a glass light pipe, a glass fiber or a transparent mica fiber.
 7. The fiber of claim 1, wherein the plurality of microelectrodes is a platinum (Pt) electrode, a palladium (Pd) electrode, or an iron (Fe) electrode containing NiS.
 8. The fiber of claim 1, wherein the plurality of microelectrodes is across the insulating layer and communicates with the inner electrode layer.
 9. The fiber of claim 1, wherein when the inner electrode layer or the outer electrode layer is used as a cathode, the material is Platinum (Pt), Palladium (Pd), Copper (Cu), aluminum (Al), Graphene, Titanium (Ti), Thallium (Tl), Chromium (Cr), or Gold (Au); when the electrode layer is used as an anode, the material is C or Ni carrying a catalyst; and the catalyst is an iron oxide, a cobalt oxide, a nickel oxide, or a mixture thereof.
 10. The fiber of claim 1, wherein the light absorbing layer is of an organic dye in the form of a divalent phosphonium salt of dicarboxybipyridine, or an organic dye mixed with an organic viscose.
 11. The fiber of claim 1, wherein the light absorbing layer is of an inorganic semiconductor material selected from TiO₂, ZnS, CdSe, MoS, CuInS or GaInP.
 12. The fiber of claim 11, wherein the inorganic semiconductor material is n-type TiO₂, ZnS or CdSe quantum dots having a particle diameter of 5 to 10 nm.
 13. The fiber of claim 1, wherein the insulating layer is of silicon dioxide, silicon nitride, polyimide or parylene.
 14. The fiber of claim 1, wherein the proton exchange membrane is a perfluorosulfonic acid membrane, a sulfonated polystyrene membrane, a modified perfluorosulfonic acid polymer membrane, or 1-butyl-3-methylimidazolium trifluoromethanesulfonate membrane.
 15. An optical cable, comprising a protective sleeve and a plurality of optical fibers of claim 1 which are axially disposed in the protective sleeve.
 16. A device, comprising an electrolytic cell, an optical cable of claim 15, an internal electrode converger, an external electrode converger, and a fiber dispersing device; wherein: one end of the first light guiding segment of the optical fiber away from the second light guiding segment is exposed out of the protective sleeve of the optical cable; one end of the second light guiding segment of the optical fiber away from the first light guiding segment is exposed out of the protective sleeve of the optical cable; the first light guiding segment of the optical fiber is dispersed by the fiber dispersing device and the one end of the first light guiding segment of the optical fiber away from the second light guiding segments immersed into the electrolyte, and the outer electrode layer of the first light guiding segment is electrically connected to the external electrode converger; and the second light guiding segment of the optical fiber is disposed outside the electrolytic cell, and the conductive layer of the second light guiding segment is electrically connected to the internal electrode converger.
 17. The device of claim 16, wherein a plurality of optical cables is disposed above the electrolytic cell in arrays.
 18. The device of claim 16, wherein the fiber dispersing device comprises a first aperture plate and a second aperture plate fixedly disposed on an upper part and a lower part of the electrolytic cell, respectively; the first aperture plate comprises a plurality of first through holes in arrays, and the second aperture plate comprises a plurality of second through holes in arrays corresponding to the first through holes in arrays; the first light guiding segment of each of the optical fibers is fixed on the first aperture plate and the second aperture plate via the first through holes and the second through holes.
 19. The device of claim 18, wherein the first aperture plate is insulated; the second aperture plate is conductive and communicates with the outer electrode layer of the first light guiding segment of each optical fiber; the internal electrode converger is a copper ring sheathed on one end of the second light guiding segment of the optical fiber, and is in contact with the conductive layer.
 20. The device of claim 16, wherein the electrolytic cell is provided with a defoaming net. 